Cf. the importance he attaches to his subject, i. 926, 'Avia Pieridum peragro loca nullius ante trita solo.' 2. His admiration for the great men of the past. Cf. iii. 1024-52, where Ancus, the Scipios, Homer, Democritus, and Epicurus are praised; the introductions to Books i., iii., v., vi., on Epicurus; i. 716-33 on Empedocles; i. 117-9 on Ennius. 3. His powers of observation and love of nature. Cf. i. 716-25; ii. 29 _sqq._, 40 _sqq._; 323-32; iv. 572 _sqq._ 4. His experience of women. Book iv. 1037-the end. 5. His wide reading. The poem shows knowledge of Epicurus, Empedocles, Democritus, Anaxagoras, Heraclitus, Plato, the Stoic writers, Thucydides, Hippocrates, Homer, Euripides. Among Latin writers Ennius, Naevius, Pacuvius, Lucilius, and Accius are all imitated. There is a reference to contemporary history in i. 41-3, 'Nam neque nos agere hoc patriai tempore iniquo possumus aequo animo nec Memmi clara propago talibus in rebus communi desse saluti.' Munro thinks that these lines were written B.C. 59, when Memmius was _praetor designatus_, in fierce opposition to Caesar, and on the side of the Senate. If this is so, the poem was probably written between B.C. 60 and 55. The lines on ambition and its attendant evils (as iii. 931 _sqq._, v. 1117-35, etc.) may have been written with a special view to the facts of Memmius' life. Lucretius may refer to his recollection of the civil wars in v. 999, 'At non multa virum sub signis milia ducta una dies dabat exitio.' In ii. 40 _sqq._ there is perhaps a reference to Caesar's army in the Campus Martius at the beginning of B.C. 58. The _de rerum natura_ is an exposition of Epicureanism, especially on its physical side; i. 54, 'Nam tibi de summa caeli ratione deumque disserere incipiam et rerum primordia pandam,' etc. The title is taken from Epicurus' περὶ φύσεως, which Lucretius followed closely, as is evident from the account of the Epicurean philosophy in Diogenes Laertius, x., and from the fragments of Epicurean writers discovered at Herculaneum in 1752. He probably used as his model Empedocles' poem περὶ φύσεως. The object of the poem is to deliver men from the fear of death and of the gods; iii. 37, 'Et metus ille foras praeceps Acheruntis agendus'; i. 62-101; cf. l. 101, 'Tantum religio potuit suadere malorum.' Note that the invocation to Venus at the beginning of the poem is not inconsistent, but is an address to the universal principle of generation; cf. i. 21, 'Quae quoniam rerum naturam sola gubernas.' The scope of the Books is as follows: Books i. and ii. state the physical theories of Democritus and Epicurus. Book i. states the Atomic Theory of Democritus, held by Epicurus, that the world consists of atoms and void. The theories of Heraclitus, Empedocles, Anaxagoras, etc. are refuted; i. 740, 'Principiis tamen in rerum fecere ruinas et graviter magni magno cecidere ibi casu.'